Tunable Magnetic Relaxation In Magnetic Nanoparticles

TL;DR

This paper studies the magnetization relaxation dynamics of conducting magnetic nanoparticles coupled to electrodes, showing how relaxation time depends on external parameters and can be measured via transport techniques.

Contribution

It introduces a method to determine magnetization relaxation time through transport measurements and explores bias-driven Brownian motion in nanoparticles.

Findings

Relaxation time $t_1$ depends on temperature, bias, and gate voltages.

Magnetization exhibits bias-driven Brownian motion under certain conditions.

Transport measurements can infer magnetization dynamics.

Abstract

We investigate the magnetization dynamics of a conducting magnetic nanoparticle weakly coupled to source and drain electrodes, under the assumption that all relaxation comes from exchange of electrons with the electrodes. The magnetization dynamics is characterized by a relaxation time $t_1$, which strongly depends on temperature, bias voltage, and gate voltage. While a direct measure of a nanoparticle magnetization might be difficult, we find that $t_1$ can be determined through a time resolved transport measurement. For a suitable choice of gate voltage and bias voltage, the magnetization performs a bias-driven Brownian motion regardless of the presence of anisotropy.